Lipotropin

Lipotropin refers to two hormones derived from pro-opiomelanocortin (POMC), which is produced in the anterior pituitary gland. These hormones are β-lipotropin (β-LPH) and γ-lipotropin, formed through the cleavage of POMC into adrenocorticotropin (ACTH) and other fragments.

β-Lipotropin is a 90-amino acid polypeptide that was initially thought to stimulate melanin production and lipid mobilization. However, subsequent studies failed to replicate these findings, and no receptor for β-LPH has been identified. It can be further cleaved into smaller peptides, including γ-lipotropin, β-melanocyte-stimulating hormone (β-MSH), and β-endorphin, the latter being a potent opioid in the pituitary gland. β-Endorphin exhibits high affinity for opiate receptors and is 100 times more potent than morphine as an analgesic.

γ-Lipotropin, composed of 56 amino acids in humans and 58 in sheep, is the amino-terminal fragment of β-LPH. It can be cleaved into β-melanocyte-stimulating hormone (β-MSH), with its carboxyl-terminal identical to that of γ-lipotropin.

Lipotropin has been associated with pain relief due to the analgesic effects of β-endorphin, which mimics morphine. It is prohibited by the World Anti Doping Agency and was implicated in controversies involving its use as AOD-9604 in Australian Rules Football, particularly in the Essendon Football Club supplements saga.

In 2020, AOD-9604 underwent clinical trials for pain treatment, highlighting its potential medical applications.